Process and apparatus for building tyres for vehicle wheels

ABSTRACT

An apparatus for building a tyre for a vehicle wheel includes a building drum having at least one first outer circumferential surface, and at least one pair of auxiliary support members removably in engagement with the building drum, each in axial side by side relationship with a respective end of the building drum and having second outer circumferential surfaces extending in the continuation of the first outer circumferential surface so as to support at least one component of the tyre. Each of the second outer circumferential surfaces has at least one non-stick circumferential portion and at least one sticking circumferential portion.

CROSS REFERENCE TO RELATED APPLICATION

This application is a divisional application of U.S. patent applicationSer. No. 13/132,302, filed Jun. 1, 2011, which is a U.S. national phaseentry under 35 U.S.C. § 371 of International PCT Application No.PCT/IB2008/055050, filed Dec. 2, 2008, the content of all of which areincorporated herein by reference.

BACKGROUND Field

The present invention relates to a process and an apparatus for buildingtyres for vehicle wheels.

More particularly, the invention applies to the process and equipmentused for building a green tyre, to be subsequently submitted to avulcanisation cycle for obtaining the final product.

Description of the Related Art

A tyre for vehicle wheels generally comprises a carcass structureincluding at least one carcass ply having respectively opposite endflaps in engagement with respective annular anchoring structures,integrated into the regions usually identified as “beads”, and having aninner diameter substantially corresponding to a so-called “fittingdiameter” of the tyre for mounting on a respective rim.

Associated with the carcass structure is a belt structure comprising oneor more belt layers, arranged in radially superposed relationship withrespect to each other and to the carcass ply and having textile ormetallic reinforcing cords with a crossed orientation and/orsubstantially parallel to the circumferential extension direction of thetyre. Applied at a radially external position to the belt structure is atread band, of elastomeric material too, like other semifinishedproducts constituting the tyre.

Respective sidewalls of elastomeric material are also applied at anaxially external position, to the side surfaces of the carcassstructure, each extending from one of the side edges of the tread banduntil close to the respective annular anchoring structure to the beads.In tyres of the “tubeless” type, an air-tight coating layer usuallyreferred to as “liner” covers the inner surfaces of the tyre.

Subsequently to building of the green tyre carried out through assemblyof the respective components, a vulcanisation and moulding treatment isgenerally performed which aims at determining the structuralstabilisation of the tyre by cross-linking of the elastomeric compoundsand also at impressing the same with a desired tread pattern and withpossible distinctive graphic marks at the sidewalls.

The carcass structure and belt structure are generally made separatelyfrom each other in respective work stations, to be mutually assembled ata later time.

In document WO2008/099236 in the name of the same Applicant, a carcassply is applied around an outer surface of a building drum, according toan application diameter greater than the fitting diameter of the tyre.Auxiliary support members, made in the form of two annular elements forexample, can be removably moved close to the building drum on axiallyopposite sides.

The auxiliary support members have respective rest surfaces preferablyhaving a substantially cylindrical conformation of substantially thesame diameter as the application diameter. The outer surface of thebuilding drum has an axial size smaller than the width of the carcassply, so that the end flaps of the carcass ply disposed on the buildingdrum axially protrude from the opposite ends of the outer surface andare at least partly supported by the aforesaid rest surfaces. Whenformation of the carcass ply/plies has been completed, the auxiliarysupport members are axially moved away from the respective halves of thebuilding drum, so that the rest surfaces can be removed from the carcassply/plies and from other possible components applied thereto. Removal ofthe rest surfaces makes it possible to fold down the end flaps of thecarcass ply/plies applied around the building drum, towards thegeometric axis of said building drum. An annular anchoring structuredefining the fitting diameter is coaxially engaged around each of theend flaps. An outer sleeve comprising at least one belt structurepossibly associated with a tread band is disposed at a coaxially centredposition around the carcass sleeve applied onto the building drum.Through axial approaching of the two halves forming the building drum,the carcass sleeve is shaped into a toroidal configuration to causeapplication of same against a radially internal surface of the outersleeve.

In the technological context in which the Applicant has to operate, anincrease in the daily productivity is often required for tyres that aredifferent from each other in size and structure, while a high operatingflexibility in the production is to be maintained.

More specifically, in this context by operating flexibility it isintended the possibility of using, for each tyre, elementary componentsthat are different from each other in terms of type of elastomericmaterial or type of textile or metallic reinforcing cord.

In the present specification and in the following claims, by the term“elementary components” it is intended to denote continuous elongatedelements of elastomeric material, rubberised textile and/or metalliccords, strip-like elements. To the aims of the present specification andthe subsequent claims, it is to be pointed out that “strip-like element”means a strip of elastomeric material cut to size and comprising one ormore textile or metallic reinforcing cords that are mutually parallel orcrossed.

In the present specification and in the following claims by “component”of a tyre it is intended any part of the tyre or a portion thereof thatis adapted to perform a function. For instance, intended as tyrecomponents are the liner, underliner, abrasion-proof element, bead core,bead filler, carcass ply, belt layer, belt underlayer, tread underlayer,under-belt inserts, sidewall inserts, sidewalls, tread band, reinforcinginserts.

In this context the Applicant has verified that an excellent quality ofthe product can be achieved by manufacturing the whole green tyrewithout removing the carcass structure from the building drum, asdescribed in the above mentioned document WO2008/099236.

SUMMARY

The Applicant has however noticed that during building of the carcassstructure a “belting” force is generated on the aforesaid supportmembers which is due to laying by spiraling of one or more continuouselongated elements of elastomeric material for example forming theliner, underliner, abrasion-proof element or other tyre components madeof elastomeric material alone. It is the Applicant's opinion that thisphenomenon takes place because during laying of the continuous elongatedelement on the respective support member, this continuous elongatedelement is pulled and deformed in an elastic manner along itslongitudinal extension and laid in this deformed configuration on thesupport member which inhibits it from recovering its originalconfiguration. The length of the continuous elongated element along theperipheral extension of the support member is therefore greater than thelength of said continuous elongated element in its originalconfiguration. The tyre components thus formed radially clench thesupport member, exerting said “belting” force thereon.

This force makes it difficult to carry out said operation of moving thesupport members away for going on building of the carcass structurecomprising at least turning up of at least one carcass ply built on thebuilding drum, which difficulty can also give rise to tearing of thematerials laid on the building drum, which will inevitably bring aboutdiscarding of the tyre being processed.

The Applicant has also observed that the presence of a non-stick surfaceon said support members, while solving the above mentioned problem,would make laying of said continuous elongated elements of elastomericmaterial very complicated within the automated scope of the aforesaidtechnological context. In fact, the laying cycle must often begin bysticking the head of the continuous elongated element to the supportmember but this adhesion cannot take place if said surface hasanti-sticking properties.

The non-stick surface of the support members would also make laying ofother components such as the so-called “square woven fabric” verycomplicated. These components, obtained from a strip-like elementcomprising a plurality of mutually crossed cords buried in a layer ofelastomeric material, do not show particular stickiness and arecompletely laid axially externally of the building drum, i.e. integrallyon said support members. These components without a manual interventionwould be unable to remain in place during their application onto saidnon-stick surface.

In the present specification and in the claims “non-stick portion” meanssuch a surface portion that an elementary component resting thereon doesnot stick on said surface portion and in addition can tangentially slidethereon without generation of frictional forces that may cause tearingor deformations capable of modifying the geometry of the elementarycomponent and consequently of the tyre component formed therefrom, outof the design parameters. For instance, these surfaces are those onwhich an added non-stick material such as “Teflon®” for example is laid,using a technology known in itself as “plasma coating”, for example.

By “sticking portion” in the present specification and in the claims itis intended a surface portion that is not provided with the abovedescribed features. At these sticking portions, the aforesaid elementarycomponent laid thereon remains in place being at least temporarily stuckon the portion itself. The sticking portions in accordance with thepresent invention are therefore of such a nature relative to theelastomeric material coming into contact with them, such as themechanically machined metal surfaces that are in no way treated or themetal base surfaces on which other (preferably metallic) material hasbeen added which has mechanical surface features (roughness, porosity,hardness) substantially identical with those of the base surface.

The Applicant has then realised that, by forming sticking portions andnon-stick portions on the outer circumferential surface of each of thesupport members, it would have been possible to build any tyre componentthereon, avoiding both the effect due to the belting force and theproblems resulting from the reduced stickiness of some elementarycomponents.

More particularly, the Applicant has found that, by making the surfaceof these support members non-stick except for at predeterminedcircumferential portions, it is possible to correctly build any tyrecomponent and easily decouple said circumferential rest surface from thetyre components built thereon, irrespective of the structure of saidcomponents, without damaging the latter or other portions of the tyrebeing processed.

More specifically, in a first aspect the present invention relates to aprocess for building tyres for vehicle wheels, comprising the steps of:

i) providing a building drum having a first outer circumferentialsurface;

ii) engaging auxiliary support members with the building drum, eachsupport member being in axially approached relationship with an axialend of the building drum, said support members each having a secondouter circumferential surface extending in the continuation of saidfirst outer circumferential surface;

wherein said second outer circumferential surface has at least onenon-stick circumferential portion and at least one stickingcircumferential portion;

iii) applying at least one tyre component around at least said secondouter circumferential surface, said tyre component lying partly on saidnon-stick circumferentially portion and partly on said stickingcircumferential portion;

iv) axially moving said auxiliary support members away from saidbuilding drum.

In a further aspect, the invention relates to an apparatus for buildingtyres for vehicle wheels, comprising:

-   -   a building drum having at least one first outer circumferential        surface;    -   at least one pair of auxiliary support members to be removably        engaged with the building drum, each in axially approached        relationship with a respective end of the building drum, and        having second outer circumferential surfaces extending in the        continuation of said first outer circumferential surface for        supporting at least one tyre component;

wherein each of the second outer circumferential surfaces has at leastone non-stick circumferential portion and at least one stickingcircumferential portion.

The Applicant has verified that the process and apparatus in accordancewith the invention enable to draw the auxiliary support members out ofthe tubular ends of the carcass sleeve already partially formed on thebuilding drum, without the friction between the second outercircumferential surface and the radially internal portions of saidtubular ends, lying in contact with said second outer circumferentialsurface, generating forces capable of damaging the carcass sleeve beingformed.

In addition, the sticking portions allow the elementary components to bestuck and maintained in place during the starting steps of laying saidcomponents on the support members and therefore enable correct laying ofall the tyre components.

The present invention, in at least one of the above aspects, can haveone or more of the preferred features hereinafter described.

In accordance with an embodiment of the process, step iii) comprises thesteps of:

iii′) sticking one starting end of a strip-like element onto thesticking circumferential portion, and

iii″) winding said strip-like element on said second outercircumferential surface.

Said strip-like element can be the so-called “square woven fabric” whichis formed with crossed cords coated with elastomeric material, is usedas a reinforcing element for the bead aiming at making the bead areastiffer, and is above all although not exclusively utilised in tyres ofthe racing type. Said strip-like element can also consist of otherreinforcing strip-like elements of different texture.

According to an alternative embodiment, step iii) comprises the stepsof:

iii′″) sticking one starting end of a continuous elongated element ofelastomeric material onto the sticking circumferential portion, and

iii^(iv)) laying said continuous elongated element of elastomericmaterial into coils disposed in side by side relationship or in at leastpartly overlapped relationship on said second outer circumferentialsurface.

Different types of elongated elements are used for example for formingthe abrasion-proof element and/or liner and/or underliner, on the drumand/or the auxiliary support members.

Preferably, the continuous elongated element of elastomeric material islaid at least partly on the strip-like element.

In fact the abrasion-proof element and liner/underliner are superposedover the “square woven fabric”.

Preferably, said sticking circumferential portion is a first stickingcircumferential portion close to the building drum.

Preferably, during said step iii), said at least one tyre component isfully laid on said second outer circumferential surface. This situationin particular can occur during laying of the “square woven fabric” andthe abrasion-proof element.

The present invention therefore allows the continuous elongated elementand/or strip-like elements and/or further elementary reinforcingcomponents to be correctly laid down, because during laying, adhesion ofthese components to the second outer circumferential surface is ensuredand at the same time separation of the already laid elongated elementfrom said second outer circumferential surface is allowed withoutrunning the risk of damaging the partly formed carcass sleeve.

In particular, the present invention prevents the adhesion between theabrasion-proof element and the second outer circumferential surface fromcausing stretching in the axial direction of the end flaps of the partlyformed carcass sleeve, during removal of the auxiliary support members.The Applicant has ascertained that in the absence of non-stick portions,this situation becomes particularly critical. In fact, if for instancethe square woven fabric is not present and the abrasion-proof elementadheres to the first outer circumferential surface of the building drumfor a portion thereof, and for the remaining portion directly adheres tothe second circumferential surface of the auxiliary members that aredevoid of non-stick portions, the pulling action exerted by theauxiliary support members during the removal step tends to separate thecoils adhering to the first outer circumferential surface of thebuilding drum from the coils adhering to the second circumferentialsurface of said auxiliary members.

Therefore, the present invention allows tyres to be manufactured thatare different from each other in terms of structure and materials of thebeads, e.g. with or without the square woven fabric, with theabrasion-proof element fully disposed on the second outercircumferential surface or partly disposed on the second outercircumferential surface and partly on the first outer circumferentialsurface of the building drum, thus improving both the production andqualitative aspects of the obtained products.

Preferably, step iii) comprises the step of laying a plurality ofstrip-like elements disposed in succession along the circumferentialextension of said first outer circumferential surface so as to form atleast one carcass ply, said step comprising the step of applying endflaps of each strip-like element onto the sticking circumferentialportion.

Preferably, said sticking circumferential portion is a 10 secondsticking circumferential portion axially spaced apart from the buildingdrum.

This solution is particularly advantageous where two heads are used forlaying the strip-like elements of the carcass ply, one head beingdisposed over the building drum and one under it. The ends of the firststrip-like elements laid on the lower portion of the drum are retainedin place and do not fall down by effect of gravity exactly due to thestickiness offered by said second circumferential portions.

Preferably, in said step iii) said second outer circumferential surfacehas a greater diameter than the fitting diameter.

Preferably, said step iv) is followed by a step v) in which a pair ofannular anchoring structures defining the fitting diameter is applied tothe end flaps of said at least one carcass ply.

Preferably, between said step iv) and step v) a step vi) is carried outin which the end flaps of said at least one carcass ply are folded downtowards a geometric rotation axis of the building drum.

Step iv) is carried out by applying a moving-apart force includedbetween about 10 kg and about 150 kg to each of said auxiliary supportmembers.

Preferably, step iv) is carried out by applying a moving-apart forcesmaller than or equal to about 100 kg to each of said auxiliary supportmembers.

Preferably, said at least one non-stick circumferential portion and atleast one sticking circumferential portion are disposed in axial side byside relationship with each other.

In addition, preferably each of the second outer circumferentialsurfaces has a first sticking circumferential portion close to a firstaxial end of the auxiliary support member.

According to a preferred embodiment, each of the second outercircumferential surfaces has a second sticking circumferential portionclose to a second axial end of the auxiliary support member opposite tosaid first axial end.

Preferably, each of the second outer circumferential surfaces has afirst non-stick circumferential portion placed on a first axial end ofthe auxiliary support member.

In addition, preferably, each of the second outer circumferentialsurfaces has a second non-stick circumferential portion placed on asecond axial end of the auxiliary support member opposite to the firstaxial end.

Preferably, the first sticking circumferential portion and the secondsticking circumferential portion are separated by a third non-stickcircumferential portion.

Sticking portions located at axially distinct points of the supportmembers allow elementary components that are to be placed at differentregions of the tyre beads to be held in place, during laying.

In more detail, applied to the first sticking circumferential portionare, for instance, the elementary components designed to form theabrasion-proof element, liner, underliner, square woven fabric.

Applied to the second sticking circumferential portion are, forinstance, the ends of the strip-like elements designed to form thecarcass ply/plies.

According to a preferred embodiment, the first sticking circumferentialportion has an axial width smaller than or equal to about 35% of anoverall axial width of the auxiliary support member.

In addition, preferably, the first sticking circumferential portion hasan axial width greater than or equal to about 20% of an overall axialwidth of the auxiliary support member.

In accordance with a preferred embodiment, the second stickingcircumferential portion has an axial width smaller than or equal toabout 15% of an overall axial width of the auxiliary support member.

In addition, preferably, the second sticking circumferential portion hasan axial width greater than or equal to about 5% of an overall axialwidth of the auxiliary support member.

In accordance with a preferred embodiment, the first non-stickcircumferential portion has an axial width smaller than or equal toabout 15% of an overall axial width of the auxiliary support member.

In addition, preferably, the first non-stick circumferential portion hasan axial width greater than or equal to about 5% of an overall axialwidth of the auxiliary support member.

In accordance with a preferred embodiment, the second non-stickcircumferential portion has an axial width smaller than or equal toabout 35% of an overall axial width of the auxiliary support member.

The choice of the size and location of the sticking portions andnon-stick portions allows tyres with different structures to be built.In addition, for building tyres of same sizes, it is sufficient toreplace the auxiliary support members alone.

Preferably, said at least one non-stick circumferential portion has aroughness smaller than or equal to about 12 μm.

The present roughness Ra is the arithmetical average value of thedeviations of the real profile of the surface from the centre line.

These values are the preferred ones in order to reduce adhesiveness asmuch as possible and increase sliding of the tyre components on thenon-stick portions, allowing easy withdrawal of the auxiliary supportmembers.

To this aim, preferably, said at least one non-stick circumferentialportion comprises a non-stick coating obtained by plasma coating.

In addition, preferably, said at least one sticking circumferentialportion has a roughness greater than or equal to about 12 μm.

Preferably, said at least one sticking circumferential portion has aroughness (Ra) smaller than or equal to about 15 μm.

These values are the preferred ones in order to give the surface thenecessary stickiness to enable temporary adhesion of the elementarycomponents during laying of same.

Preferably, said at least one non-stick circumferential portion and saidat least one sticking circumferential portion delimit a step betweenthem the thickness of which is included between about 5 μm and about 50μm.

In addition, preferably, said thickness is thinner than or equal toabout 20 μm.

The limited thickness of the step prevents the engagement of the tyrecomponents directly in contact with the step itself during removal ofthe auxiliary support members from damaging the tyre and/or makingremoval difficult.

Further features and advantages will become more apparent from thedetailed description of a preferred but not exclusive embodiment of aprocess and an apparatus for building tyres for vehicle wheels, inaccordance with the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

This description will be set out hereinafter with reference to theaccompanying drawings, given by way of non-limiting example, in which:

FIG. 1 diagrammatically shows, in diametrical section, a step ofapplying a carcass ply around a building drum provided with twoauxiliary support members in accordance with the building process of thepresent invention;

FIG. 2 is a perspective view to an enlarged scale relative to FIG. 1, ofone of the auxiliary support members;

FIG. 3 shows an enlarged portion of one of the auxiliary support membersseen in FIG. 1;

FIG. 3a is a further enlargement of FIG. 3;

FIG. 4 shows the portion in FIG. 3 on which tyre components are laid, inaccordance with an alternative embodiment of the building processaccording to the present invention;

FIG. 5 shows to an enlarged scale relative to FIG. 1, a step in whichannular anchoring structures are coaxially fitted on the respective endflaps of the carcass ply/plies;

FIG. 6 shows a tyre being processed in the step during which the carcasssleeve is shaped for application of an outer sleeve thereto.

DETAILED DESCRIPTION

With reference to the drawings, an apparatus for building tyres forvehicle wheels designed to put into practice a process according to thepresent invention has been generally identified by reference numeral 1.

Apparatus 1 is intended for manufacture of tyres 2 (FIG. 6) essentiallycomprising at least one carcass ply 3 preferably internally coated witha layer of impermeable elastomeric material referred to as “liner” 4.Two annular anchoring structures 5, each comprising a so-called beadcore 5 a preferably carrying an elastomeric filler 5 b at a radiallyexternal position, are in engagement with respective end flaps 3 a ofthe carcass ply or plies 3. The annular anchoring structures 5 areintegrated close to regions usually identified with the name of “beads”6, at which usually engagement between a tyre 2 and the respectivemounting rim (not shown) occurs, according to a fitting diameter “D0”determined by the inner diametrical sizes of the annular anchoringstructures 5 (FIG. 5).

A belt structure 7 is circumferentially applied around the carcassply/plies 3 and a tread band 8 circumferentially overlaps the beltstructure 7. Two sidewalls 9, extending each from the corresponding bead6 to a corresponding side edge of the tread band 8, are applied to thecarcass ply/plies 3, at laterally opposite positions.

Apparatus 1 comprises a substantially cylindrical building drum 10having two halves 10 a supported by a central shaft 11 extending along ageometric axis “X-X” of the building drum 10. Halves 10 a can be axiallyapproached, upon command of a threaded bar 12 for example, that isoperatively disposed within the central shaft 11 and carries twothreaded portions 12 a, 12 b, i.e. a right-handed portion and aleft-handed portion respectively, each of them engaging one of halves 10a. Halves 10 a of the building drum 10 are consequently induced tosimultaneously translate in respectively opposite directions along thecentral shaft 11, following rotations imparted to the threaded bar 12 byan actuator (not shown) that can be operatively coupled to one end ofthe central shaft 11.

The building drum 10 can further comprise a central section 13 slidablyengaging halves 10 a and extending in surface continuity relationshiprelative to said halves so as to define therewith, at a radiallyexternal position, a first outer circumferential surface 14 that issubstantially continuous.

Each of halves 10 a and the central section 13 are made up of respectivecircumferential sectors that are radially movable between a restcondition (not shown) at which they are moved radially close to thegeometric axis “X-X” to give the building drum 10 an overall diametricaldimension smaller than the fitting diameter “D0” of the tyre beingprocessed, in order to enable removal of the tyre 2 being processed fromsaid building drum, and a work condition at which, as shown in thedrawings, they extend in circumferential continuity relationship so asto form said outer surface 14 defining an application diameter “D1”preferably greater than the fitting diameter “D0” (FIG. 5).

The building drum 10 lends itself to be transferred, by at least onerobotized arm (not shown) or transfer devices of other type acting on atleast one grip end 11 a exhibited by the central shaft 11, to one ormore work stations to allow accomplishment of different working stepsaiming at assembling the tyre 2 being processed.

More particularly, the building drum 10 for instance can be firstengaged in a building station 15 (FIGS. 1 to 5) in which a so-calledcarcass sleeve is made, which comprises the carcass ply/plies coupled tothe respective annular anchoring structures 5.

At least one outer handling device (not shown as made in known manner)carries out positioning of the auxiliary support members 16, made in theform of two annular elements for example (FIG. 2), in axially approachedrelationship with the building drum 10 on axially opposite sides.

The auxiliary support members 16 have respective second outercircumferential surfaces 16 a preferably shaped into a substantiallycylindrical conformation of substantially the same diameter as theapplication diameter “D1”. When approaching has occurred, the secondouter circumferential surfaces 16 a extend in continuity relationship inthe continuation of the first outer circumferential surface 14.

Engagement of the auxiliary support members 16 with the building drum 10takes place at respective connecting members 17 carried by the buildingdrum 10, made each in the form of a cylindrical sleeve for example,integrally carried by one of halves 10 a of the building drum 10 andadapted to be operatively associated with an engagement seat 18 carriedby the respective auxiliary support member 16.

Fitting elements, not shown, lend themselves to automatically engage therespective connecting members 17, so as to retain each auxiliary supportmember 16 in engagement relationship with the building drum 10 alsoafter said members 17 have been disengaged from the aforesaid outerhandling device.

The building drum 10 is thus adapted to be transferred, if necessary,between at least one first and one second work unit (not shown) providedin the building station 15, together with the auxiliary support members16 linked thereto.

Operating in the building station 15 are auxiliary devices (not shown),adapted to apply components of the carcass sleeve to the building drum10.

The carcass ply/plies 3 and/or other parts of tyre 2 are preferably madethrough laying of one or more elementary components. These elementarycomponents are adapted to be used in a suitable amount in order to makeup one or more of the above described constituent elements of the tyre,without storage of semifinished products being required.

In more detail, for instance, these auxiliary devices may comprise oneor more dispensing devices supplying at least one continuous elongatedelement of elastomeric material while the building drum 10 is beingdriven in rotation about its geometric axis “X-X”, so as to form saidliner 4 and/or underliner on the first outer circumferential surface 14and the second outer circumferential surfaces 16 a.

In addition or as an alternative to liner 4 and/or the underliner, theauxiliary devices can be set to form further components on the secondouter circumferential surfaces 16 a, such as the abrasion-proof element19 to be incorporated at the beads 6, and/or to lay strip-like elements20 forming reinforcing fabrics such as the square-woven fabric, and/or,in the case of the so-called run-flat tyres, to lay auxiliary supportinserts made of elastomeric material alone (the so-called sidewallinserts) applied onto the respective halves 10 a of the building drum10, so that they are then incorporated at the inside of tyre 2 in thesidewall region 9.

As shown in FIGS. 1, 3, 5 and 6, before laying of liner 4, a continuouselongated element is laid in the form of coils disposed in side by siderelationship or radially superposed internally of the second outercircumferential surface 16 a, so as to form the abrasion-proof element19.

According to an alternative construction of the carcass structure, notshown, the abrasion-proof element 19 is laid starting from the firstouter circumferential surface 14 of drum 10 as far as the second outercircumferential surface 16 a and therefore it lies astride the two abovementioned surfaces 14, 16 a.

As shown in FIG. 4, before laying of the abrasion-proof element 19, thestrip-like element (forming the square-woven fabric) 20 is fully laid onthe second outer circumferential surface 16 a.

Subsequently to formation of the above-mentioned components 4, 19, 20,devices not shown as they can be made in any convenient manner, applythe carcass ply/plies 3 around the first outer circumferential surface14, according to said application diameter “D1”. Each carcass ply 3 canconsist of an article of manufacture in the form of a continuous strippreviously cut according to the circumferential extension of the firstouter circumferential surface 14 and fed towards the latter, while thebuilding drum 10 is rotating around its geometric axis “X-X”, so as tocause winding of said strip around said first outer circumferentialsurface 14.

Alternatively, according to a preferred embodiment, the applicationdevices comprise members for sequentially applying a plurality ofstrip-like elements disposed transversely of the circumferentialextension of the first outer circumferential surface 14, while thebuilding drum 10 is being driven in rotation in a step-by-step movement,in the same manner as described in the U.S. Pat. No. 6,328,084 in thename of the same Applicant, for example.

The carcass ply/plies 3 are then preferably formed directly on thebuilding drum 10, by the strip-like elements applied in mutuallyapproached relationship so as to cover the whole circumferentialextension of the first outer circumferential surface 14.

Preferably, the first outer circumferential surface 14 has a smalleraxial size than the width of said at least one carcass ply 3, so thatthe carcass ply/plies 3 laid on the building drum 10 axiallyprotrudes/protrude from the opposite ends of the first outercircumferential surface 14 and appears/appear to be at least partlysupported, together with liner 4 and/or the underliner and/or theabrasion-proof element 19 and/or the square-woven fabric 20, by theabove mentioned second outer circumferential surfaces 16 a belonging tothe auxiliary support members 16.

In the embodiment shown in the accompanying drawings, each of theauxiliary support members 16 comprises a tubular body 21 delimiting theengagement seat 18 with the connecting member 17 carried by the buildingdrum 10. When the auxiliary support member 16 is engaged to the buildingdrum 10, the geometric axis “X-X” of the building drum 10 is coincidentwith the main axis “Y-Y” of the tubular body 21.

The auxiliary support member 16 further comprises a radially externalcylindrical body 22, spaced apart from and coaxial with the tubular body21 and connected to the latter through a circular plate 23. Thecylindrical body 22 has a first circular edge 24 a which approaches thebuilding drum 10 when the auxiliary support member 16 is in engagementwith the building drum 10.

The second outer circumferential surface 16 a lies on the cylindricalbody 22 and has non-stick circumferential portions 25′, 25″, 25′″ andsticking circumferential portions 26′, 26″. Said non-stickcircumferential portions 25′, 25″, 25′″ and sticking portions 26′, 26″have a cylindrical shape coaxial with the main axis “Y-Y”.

In the embodiment shown not in a limiting sense, three non-stickcircumferential portions 25′, 25″, 25′″ are disposed in side by siderelationship and alternated along the axial extension of the auxiliarysupport member 16, with two sticking circumferential portions 26′, 26″.

Preferably, as shown, each of the second outer circumferential surfaces16 a has a first sticking circumferential portion 26′ close to a firstaxial end 27 of the auxiliary support member 16 carrying the circularedge 24 a and a second circumferential sticking portion 26″ close to asecond axial end 28 opposite to said first axial end 27.

Each of the second outer circumferential surfaces 16 a further has afirst non-stick circumferential portion 25′ placed on the first axialend 27 of the auxiliary support member 16, a second non-stickcircumferential portion 25″ placed on the second axial end 28 of theauxiliary support member 16 and a third non-stick circumferentialportion 25′″ interposed between the first 26′ and second 26″ stickingcircumferential portion.

The first non-stick circumferential portion 25′ extends in an axialdirection starting from the first circular edge 24 a towards the secondaxial end 28 as far as the first sticking circumferential portion 26′.The first sticking circumferential portion 26′ extends in an axialdirection starting from the first non-stick circumferential portion 25′towards the second axial end 28 as far as the third non-stickcircumferential portion 25′″. The third non-stick circumferentialportion 25′″ extends in an axial direction starting from the firststicking circumferential portion 26′ towards the second axial end 28 asfar as the second sticking circumferential portion 26″. The secondsticking circumferential portion 26″ extends in an axial directionstarting from the third non-stick circumferential portion 25′″ towardsthe second axial end 28 as far as the second non-stick circumferentialportion 25″. The second non-stick circumferential portion 25″ extendsstarting from the second sticking circumferential portion 26″ as far asa second circular edge 24 b lying on the second axial end 28 of theauxiliary support member 16.

Given the overall width “L” of the auxiliary support member 16, measuredalong a direction parallel to the main axis “Y-Y”, the first non-stickcircumferential portion 25′ has an axial width “L1” included betweenabout 5% and 15% of the overall axial width “L” of the auxiliary supportmember 16.

The first sticking circumferential portion 26′ has an axial width “L₂”included between about 20% and 35% of said overall axial width “L” ofthe auxiliary support member 16.

The second sticking circumferential portion 26″ has an axial width “L₃”included between about 5% and 15% of the overall axial width “L” of theauxiliary support member 16.

The second non-stick circumferential portion 25″ has an axial width “L₄”smaller than or equal to about 35% of the overall axial width “L” of theauxiliary support member 16. The second non-stick circumferentialportion 25″ therefore can also be absent.

Each of the non-stick circumferential portions 25′, 25″, 25′″ mustenable relative sliding of the carcass sleeve components of the tyreunder processing substantially without offering any resistance.

Preferably, this result is obtained by laying a non-stick coating(containing Teflon®, for example) on the cylindrical body 22, preferablyusing the known plasma-coating technique.

Following laying of the coating, the non-stick circumferential portions25′, 25″, 25′″ preferably have a roughness “Ra” smaller than or equal toabout 12 Each of the sticking circumferential portions 26′, 26″ mustallow the elementary components to be stuck and maintained in placeduring the starting steps of laying the same on the auxiliary supportmembers 16.

To this aim, these sticking circumferential portions 26′, 26″ preferablyhave a roughness “Ra” included between about 12 μm and about 15 μm.

The sticking portions 26′, 26″ are submitted to mechanical machiningoperations alone without any added material being laid or with laying ofadded material having mechanical surface features substantiallyidentical (roughness, porosity, hardness) with those of the basesurface.

In a preferred embodiment, one or more layers of metal material areadded on the whole radially external surface of the cylindrical body 22.These layers have a dual function: ensuring the intimate adhesion of afinal non-stick added coating, of Teflon® for example, on the non-stickcircumferential portions 25′, 25″, 25′″; and offering the desired“adhesiveness” of the sticking circumferential portions 26′, 26″.

By laying the metal material layers on the non-stick circumferentialportions 25′, 25″, 25′″ as well, it is also possible to limit thethickness “s” of the step (FIG. 3a ) that is formed between a non-stickcircumferential portion 25′, 25″, 25′″ and an adjacent stickingcircumferential portion 26′, 26″ to values lower than 50 μm. Preferably,this thickness is included between about 5 μm and about 20 μm.

As shown in FIGS. 1, 3, 5 and 6, a starting end of the continuouselongated element is first stuck to the first sticking circumferentialportion 26′, which continuous elongated element is subsequently laid inthe form of coils disposed in side by side relationship or at leastpartly radially superposed, to form the abrasion-proof element 19.

As shown in FIG. 4, before laying the abrasion-proof element 19, astarting end of the strip-like element is stuck to the first stickingcircumferential portion, which strip-like element is then wound up toform the square-woven fabric 20.

As shown in FIGS. 1, 3, 4, 5 and 6, stuck to the second stickingcircumferential portion 26″ are the end flaps 3 a of the strip-likeelements disposed transverse to the circumferential extension of thefirst outer circumferential surface 14 and designed to form the carcassply/plies 3.

When formation of the carcass ply/plies 3 has been completed, theauxiliary support members 16 are disengaged from the respectiveconnecting members 17. This disengagement can be for example obtainedwith the aid of the aforesaid outer handling device, by an actioninvolving axial moving apart from the respective halves 10 a of thebuilding drum 10 so as to remove the second outer circumferentialsurfaces 16 a from the abrasion-proof element 19, and/or liner 4, and/orsquare-woven fabric 20 and/or carcass ply/plies 3.

When disengagement is over, the auxiliary support members 16 can remainin engagement with the outer handling device, ready for being used againin a new working cycle.

During disengagement, a moving-apart force depending on the tyre sizeand type is applied to each of said auxiliary support members 16. Thisforce is included between about 10 kg and about 150 kg and in any caseis preferably lower than 100 kg.

Removal of the auxiliary support members 16 makes it possible, afterpossible transfer of the building drum 10 to another working unit, tofold down the end flaps 3 a of the carcass ply/plies 3 applied aroundthe building drum, towards the geometric axis “X-X” of the building drumitself, for instance with the aid of rollers or other devices not shownas they can be made in any convenient manner.

Locating members, not shown as they can be made in known manner, carryout fitting of each of the annular anchoring structures 5 coaxiallyaround one of the end flaps 3 a of the carcass ply/plies 3 folded downtowards the geometric axis “X-X”, locating it in axial abutmentrelationship against the corresponding half of the building drum 10(FIG. 5).

When the locating operation has been completed, turning-up members, notshown, turn up each of the end flaps 3 a around the respective annularanchoring structure 5, so as to stabilise engagement of same with thecarcass ply/plies 3 giving rise to formation of said carcass sleeve.

When engagement of the annular anchoring structures 5 is over orconcurrently with this operating step, application of at least oneportion of the sidewalls 9 can be carried out.

The building drum 10 carrying the carcass sleeve is then preferablytransferred to a location 29 (FIG. 6) external to the building station19, for receiving and engaging an outer sleeve 30 integrating the beltstructure 7, preferably already coupled to the tread band 8.

The outer sleeve 30 having an inner diameter “D2” greater than thewinding diameter “D1”, can be prepared in advance by formation orwinding of one or more belt layers adapted to make the belt structure 7on an auxiliary drum (not shown), and subsequent winding of the treadband 8 on the belt structure 7 carried by the auxiliary drum. Moreparticularly, building of the tread band 8 can be carried out by feedingmeans supplying a continuous elongated element of elastomeric materialthat is applied, in the form of coils disposed in side by siderelationship and/or at least partly radially superposed, onto the beltstructure 7 carried by the auxiliary drum, while the latter is beingdriven in rotation. According to an alternative embodiment, at the endat least one portion of the sidewalls 9 can be build on the outer sleeve30.

The outer sleeve 30 thus formed is adapted to be removed from theauxiliary drum, for instance by means of a transfer ring 31 or othersuitable devices that will then dispose it to a coaxially centredposition around the carcass sleeve carried by the building drum 10.

Then, shaping devices act on the building drum 10 to shape the carcasssleeve into a toroidal configuration, so as to cause application of sameagainst a radially internal surface of the outer sleeve 30.

The shaping devices can for instance comprise said actuator (not shown)designed to drive the threaded bar 12 in rotation to cause mutual axialapproaching of halves 10 a of the drum and, consequently, of the annularanchoring structures 5 of the carcass sleeve. Preferably, the shapingdevices further comprise inflating members, not shown, adapted to feed aworking fluid into the carcass sleeve and cause radial expansion thereofby inflation, during mutual approaching of the annular anchoringstructures 5.

Then at least one auxiliary shaping member 32 (only diagrammaticallyshown in FIG. 6) is preferably engaged to the building drum 10, whichauxiliary member is suitable for being integrated with the shapingdevices to enable the shaping step of the carcass sleeve to be carriedout.

When the shaping step has been completed, the building drum 10 can bepossibly transferred to at least one additional working station (notshown).

At the end of building, tyre 2 can be removed from the building drum 10after disengagement of the auxiliary shaping members 32 and radialcontraction of said drum, to be submitted to a vulcanisation andmoulding step to be carried out in any convenient manner.

The invention claimed is:
 1. An apparatus for building a tyre for avehicle wheel, comprising: a building drum having at least one firstouter circumferential surface; and at least one pair of auxiliarysupport members configured to be removably engaged with the buildingdrum, each in axially approached relationship with a respective end ofthe building drum and having second outer circumferential surfacesextending in a continuation of said first outer circumferential surfacefor supporting at least one component of the tyre, wherein each of thesecond outer circumferential surfaces has a plurality of non-stickcircumferential portions and a plurality of sticking circumferentialportions, the non-stick and sticking portions arranged in an alternatingmanner along the axial extension of each auxiliary support member andcomprising a first sticking circumferential portion having an axialwidth of between about 20% and about 35% of an overall axial width ofone of said auxiliary support members.
 2. The apparatus as claimed inclaim 1, wherein said first sticking circumferential portion ispositioned near a first axial end of the auxiliary support member. 3.The apparatus as claimed in claim 2, wherein each of the second outercircumferential surfaces has a second sticking circumferential portionnear a second axial end of the auxiliary support member opposite saidfirst axial end.
 4. The apparatus as claimed in claim 3, wherein each ofthe second outer circumferential surfaces has a first non-stickcircumferential portion placed on a first axial end of the auxiliarysupport member.
 5. The apparatus as claimed in claim 4, wherein each ofthe second outer circumferential surfaces has a second non-stickcircumferential portion placed on a second axial end of the auxiliarysupport member opposite the first axial end.
 6. The apparatus as claimedin claim 5, wherein the first sticking circumferential portion andsecond sticking circumferential portion are separated by a thirdnon-stick circumferential portion.
 7. The apparatus as claimed in claim3, wherein the second sticking circumferential portion has an axialwidth smaller than or equal to about 15% of an overall axial width ofthe auxiliary support member.
 8. The apparatus as claimed in claim 3,wherein the second sticking circumferential portion has an axial widthgreater than or equal to about 5% of an overall axial width of theauxiliary support member.
 9. The apparatus as claimed in claim 4,wherein the first non-stick circumferential portion has an axial widthsmaller than or equal to about 15% of an overall axial width of theauxiliary support member.
 10. The apparatus as claimed in claim 4,wherein the first non-stick circumferential portion has an axial widthgreater than or equal to about 5% of an overall axial width of theauxiliary support member.
 11. The apparatus as claimed in claim 5,wherein the second non-stick circumferential portion has an axial widthsmaller than or equal to about 35% of an overall axial width of theauxiliary support member.
 12. The apparatus as claimed in claim 1,wherein said plurality of non-stick circumferential portions have aroughness smaller than or equal to about 12 μm.
 13. The apparatus asclaimed in claim 1, wherein said plurality of non-stick circumferentialportions comprise a non-stick coating obtained by plasma coating. 14.The apparatus as claimed in claim 1, wherein said plurality of stickingcircumferential portions have a roughness greater than or equal to about12 μm.
 15. The apparatus as claimed in claim 1, wherein said pluralityof sticking circumferential portions have a roughness smaller than orequal to about 15 μm.
 16. The apparatus as claimed in claim 1, whereinat least one of said plurality of non-stick circumferential portions andat least one of said plurality of sticking circumferential portionsdefine a step therebetween, the thickness of which is between about 5 μmand about 50 μm.
 17. The apparatus as claimed in the claim 16, whereinsaid thickness is less than or equal to about 20 μm.